CN102339609A - Disk drive preamplifier frequency-response and time delay compensation - Google Patents

Abstract

The invention discloses disk drive preamplifier frequency-response and time delay compensation. An apparatus including one or more reader circuits, one or more writer circuits, and a loopback channel. The one or more reader circuits may be configured to read data from a magnetic medium. The one or more writer circuits may be configured to write data to the magnetic medium. The loopback channel is coupled between the one or more reader circuits and the one or more writer circuits.

Description

Frequency response of disk file prime amplifier and compensation of delay

Technical field

Generally speaking, the present invention relates to be used for the system and method for access storage media, particularly, relate to the method and/or the device that are used to realize frequency response of disk file prime amplifier and compensation of delay.

Background technology

Be included in storage medium to be written to the magnetic storage medium writing information and nearby generate magnetic field.In the conventional memory storage that uses magnetic medium, use conventional read/write head stack nearby to generate magnetic field at magnetic storage medium.The read/write head stack can comprise induction write element and magnetic resistance (MR) read element.Information to be stored is sent to and writes/coding circuit.Write/coding circuit encodes to information, thereby storage efficiency maximized.Write then ,/coding circuit regulates the electric current in the write head, makes the magnetic field of the magnetized alternating polarity of storage medium with generation.The quality of writing information depends on the suitable spacing (being flying height) between write head and the medium to a great extent.

With reference to figure 1, the figure shows the read/write head stack 10 that is provided with respect to storage medium 12, as the mode of describing magnetic flying height (or spacing) 14.Usually, the distance between read/write head stack 10 and the storage medium 12 is commonly referred to flying height.During reading, require suitably control flying height, show signal to noise ratio (S/N ratio) as well as possible to guarantee read back waveform, thereby improve performance, prevent the head disk contact that is harmful to.Usually, flying height is used to represent magnetic flying height 14.Magnetic flying height 14 is generally corresponding to the spacing of the converter pole tip of magnetic film on the storage medium 12 and read/write head stack 10.But; Because applying and lubricate, the head surface of read/write head stack 10 and storage medium 12 protectiveness ground layer is arranged (promptly; Be respectively coating 16 and 18) with anticorrosion and alleviate instantaneous head disk and contact the infringement that causes, so physics flying height (or spacing) 20 with the gross thickness of coating 16 and 18 less than magnetic flying height 14.

In conventional disk file, flying height is confirmed through two or more harmonic amplitude of measuring read back waveform.Free time or the reserved area on the magnetic storage medium of (therefrom can measure harmonic wave) periodic pattern used and to be comprised to conventional method.Though conventional method provides the reasonable static of flying height to estimate that conventional method can't be provided at the indication of any variation of the flying height that takes place in the accurate running time section.Therefore, conventional method can't provide the ability of the variation that is adjusted at magnetic storage medium operating period generation.For the part alleviates the ineffectivity of orthodox flight height measurement scheme, so as control to write for a long time or data transmission procedure in flying height, can be used as the retaking of a year or grade harmonic source with the staggered servo-information of data.

Depend on accurate understanding based on the orthodox flight height measurement method of harmonic amplitude sensing to (comprising prime amplifier and recording channel mimic channel and interconnected transmission line) read back waveform path gain.Other measurement of flight altitude methods for example based on those methods of channel bit density (CBD) estimation and full read back waveform amplitude, can show the susceptibility to change in gain at the CF place, therefore can benefit from these frequency places and make gain stabilization.

The measurement of flight altitude precision is subject to the inevasible drift of the amplitude response of prime amplifier, and is arranged in the fetch channel analog part.Even in the device of current techniques development level, the measurement of flight altitude precision the below～4nm spacing is also very poor.Take place in patterned media on the throne (BPM) record further about the problem of tolerance, wherein seek to write accurate aligning of the pre-deposition platform (land) on conversion and the storage medium.In this logging mode, very crucial to the compensation that the delay of reading write paths that comprises prime amplifier and recording channel changes.A kind of method that compensation delay changes is used the multiple read of the periodicity emphasis in the presumptive area, to confirm to produce the write phase of maximum playback amplitude.But this kind method has reduced average file transfer rate.

In order in device lifetime, to keep constant relative gain, expect a kind of method and/or device of measuring and/or compensate the variation in the prime amplifier frequency response at the CF place at the CF place.Also being desirably in provides a kind of and measures prime amplifier and passage reads the method and/or the device of the total delay of write paths in the BPM register system, so that allow to postpone compensating for variations.

Summary of the invention

The present invention relates to a kind of device that comprises one or more reading magnetic head element circuits, one or more write head element circuit and loopback channel.One or more reading magnetic head element circuits can be configured to from the magnetic medium reading of data, and wherein, this reading of data is present in the read back waveform after the amplification.One or more write head element circuits can be configured to write data to magnetic medium.Loopback channel is coupled between one or more reading magnetic head element circuits and the write head element circuit.

Further, loopback channel comprises: the loopback reader unit is connected to one or more reading magnetic head element circuits; The luffing current switch is connected to the loopback reader unit; And selector unit, be connected to luffing current switch and one or more write head element circuit.

Further, loopback channel also comprises: the loopback writing unit is connected to selector unit and one or more write head element circuit.

Further, the luffing current switch comprises electric current route long-tail pair.

Further, loopback channel comprises: the loopback reader unit is connected to one or more reading magnetic head element circuits; And loopback injection and gain control circuit, be connected to the write paths of loopback reader unit and device.

Further, loopback channel also comprises: a pair of operation transconductance amplifier, being configured to provides common mode ground connection to the loopback reader unit, and zero clearing loopback cell passage output before appearing at one or more reading magnetic head element circuits.

Further, loopback injection and gain control circuit comprise the Origami cascaded circuit of complementary bipolar.

A kind of device comprises: one or more id reader circuit are configured to from the magnetic medium reading of data; One or more write device circuit are configured to data are write to magnetic medium; And loopback channel, be coupled between one or more id reader circuit and the one or more write device circuit, wherein, loopback channel uses complementary SiGe BiCMOS to handle and implements.

Further, loopback channel for double frequency measurement of flight altitude launch, and during normally reading write operation, forbid.

Further, one or more reading magnetic head element circuits and one or more write head element circuit are forbidden during the double frequency measurement of flight altitude.

A kind of method may further comprise the steps: measurement is read the prerecord calibration region of magnetic storage medium simultaneously in the amplitude of two frequencies of output place of prime amplifier; Launch the loop back mode of prime amplifier, and inject the Composite Double frequency sequence on the data line writing of prime amplifier; When the Composite Double frequency sequence be injected into prime amplifier write on the data line time, be recorded in the amplitude of two frequencies of output place of prime amplifier; And use the playback amplitude after amplitude that (i) measure, the amplitude that (ii) writes down in the loop back mode and (iii) predetermined baseline loopback value are come calculation correction when reading the prerecord calibration region.

Further, predetermined baseline loopback value is stored in the disc file unit that comprises magnetic medium.

Further, this method also comprises: use correction back playback amplitude and Wallace's space loss equation to calculate the flying height error with respect to the predetermined set-points flying height.

Further, this method also comprises: will with respect to behind the flying height compensation of error of set point and the calibration after form be applied to the heater driver element, so that flying height is adjusted to predetermined set-points.

Further, this method also comprises: the step of claim 11 is repeated more than twice or twice.

Further, predetermined loopback baseline value is confirmed in factory in the following manner: reading magnetic head is moved on the prerecord calibration region of magnetic storage medium; Control head is retreated magnetic head to the predetermined set-points flying height with near the landing point then; At predetermined set-points flying height place, measure two amplitudes, and forever preserve measured amplitude in two frequencies of output place of prime amplifier; Launch the loop back mode of prime amplifier, and inject the Composite Double frequency sequence on the data line writing of prime amplifier; When the Composite Double frequency sequence be injected into prime amplifier write on the data line time, be recorded in the amplitude of two frequencies of output place of prime amplifier; And the amplitude that is write down saved as predetermined loopback baseline value.

Further, under specified environment, measure predetermined value.

Further, the point that lands carries out sensing through the vibration that superposes on the track position error signal or through auxiliary acoustic sensor or thermal sensor.

A kind of device comprises: one or more id reader circuit are configured to from the magnetic medium reading of data; One or more write device circuit are configured to data are write magnetic medium; And loopback channel; Be coupled between one or more id reader circuit and the one or more write device circuit; Loopback channel comprises the loopback injection and the gain control circuit of loopback reader unit that is connected to one or more id reader circuit and the write paths that is connected to loopback reader unit and device; Wherein, this loopback injection and gain control circuit comprise the Origami cascaded circuit of complementary bipolar.

A kind of device comprises: one or more id reader circuit are configured to from the magnetic medium reading of data; One or more write device circuit are configured to data are write magnetic medium; And loopback channel; Be coupled between one or more id reader circuit and the one or more write device circuit, wherein, loopback channel comprises; Be connected to the loopback reader unit of one or more id reader circuit; And a pair of operation transconductance amplifier, operation transconductance amplifier is configured to the loopback reader unit common mode ground connection is provided, and zero clearing loopback cell passage output before appearing at one or more id reader circuit.

The object of the invention, characteristic and advantage comprise: a kind of method and/or device of realizing frequency response of disk file prime amplifier and compensation of delay is provided; This method and/or device can (i) provide a kind of loopback channel that allows the prime amplifier frequency response in the sign at institute selected frequency place; (ii) measure and compensate the variation in the prime amplifier frequency response; So that in device lifetime, keep constant relative gain at the CF place, the gain stability of measurement of flight altitude technology (iii) is provided based on the relative amplitude of playback tone, (iv) allow the field of reader frequency response to characterize; (v) derive correction coefficient; To remove change in gain, (vi) allow to measure the timing that writes data to reading of data, (vii) support bit-patterned medium (BPM) record; (viii) compensate prime amplifier write with read path in delay change, and/or the areas of applicability that (ix) disc driver is read-write prime amplifier extends to Tb/in ²The surface density rank.

Description of drawings

Based on following detailed description and accompanying claims and accompanying drawing, above-mentioned and other purposes, characteristics and advantage of the present invention will become obviously, among the figure:

Fig. 1 is the read/write head stack that illustrates with respect to the storage medium configuration, to describe the diagrammatic sketch of magnetic flying height and physics flying height;

Fig. 2 is the block diagram that the magnetic recording system that comprises prime amplifier according to the embodiment of the present invention is shown;

Fig. 3 is the Line Chart that the admissible differential gain error of various flying heights is shown;

Fig. 4 is the block diagram of the illustrative embodiments of the prime amplifier among the Fig. 2 that illustrates according to the embodiment of the present invention;

Fig. 5 is the block diagram that the illustrative embodiments of the prime amplifier among Fig. 4 is shown;

Fig. 6 is the block diagram that the illustrative embodiments of the loopback circuit block among Fig. 5 is shown;

Fig. 7 is the block diagram of another illustrative embodiments of the prime amplifier among the Fig. 2 that illustrates according to another implementation of the invention;

Fig. 8 is the block diagram that the illustrative embodiments of the loopback circuit among Fig. 7 is shown;

Fig. 9 is the diagrammatic sketch that the illustrative embodiments of the loopback gain block among Fig. 8 is shown;

Figure 10 is the diagrammatic sketch that the instance of reading magnetic head unit according to the embodiment of the present invention is shown;

Figure 11 A and Figure 11 B are the diagrammatic sketch that the instance of loopback zero clearing piece according to the embodiment of the present invention is shown;

Figure 12 is the curve map that illustrates according to the contrast between the differential gain error of the exemplary prime amplifier that comprises and do not comprise loopback compensation of the present invention;

Figure 13 illustrates the double frequency measurement of flight altitude that comprises that loopback compensates according to the present invention to handle

The process flow diagram of instance;

Figure 14 is the process flow diagram that the processing of the baseline value that uses in the processing of confirming Figure 13 is shown.

Embodiment

Reproduce head in the disk file can be used as flying height (FH) converter in vertical and longitudinal recording.Though embodiment may change, basic theme comprises that application and Wallace's space loss equation of at least two different frequencies are to infer flying height.The use of a plurality of frequencies allows the read path entire gain to change and measurement of flight altitude decoupling mutually.But the gain ratio of institute's selected frequency generally need keep substantially constant in life of product.At the approaching 1Tbit/in that also surpasses ²During density, low flying height and be major consideration to the accurate control of head disk spacing.

The disk file prime amplifier can be made up of one or more front ends (or reading magnetic head unit) low noise amplifiers (LNA) and the magnetic resistance that is associated (MR) magnetic head biasing injection circuit.Each magnetic head unit can be served the specific record magnetic head.Magnetic head select command as from the system data controller is pointed, can activate single reading magnetic head unit.The output of magnetic head unit can arrive recording channel then through gain and signal Processing level public concerning all magnetic heads.Equally, one group of write head unit can be set.Each write head unit possibly be associated with specific write head.All write head unit can provide service by one group of (receive from recording channel write the data inputs) signal processing electronic device.The present invention provides generally and reads that illusory (or loopback) writes loopback and read loopback cell like the write head unit class.Writing loopback and reading loopback cell does not provide magnetic head, and links together, thereby writes data through public write device circuit, through loopback cell; Be back to recording channel through the public electronic installation that reads.In optional embodiment, can carry out through related internal bridgt circuit with the read/write magnetic head unit is provided according to loop back function of the present invention.

Usually, the present invention provides Method and circuits, generating correction coefficient, so that prime amplifier read path relative gain normalization again, thereby compensating element, is aging and environmental change.Under the situation that does not have again normalization, it is difficult using the auxiliary multi-frequency technology of nothing to obtain accurate flying height sensing.The further benefit of the prime amplifier of implementing according to the present invention is to have the function that the relative gain in the ASH element of proofreading and correct the prime amplifier downstream changes.For example, can measure and compensate the prime amplifier frequency response change according to the embodiment of the present invention, so that in device lifetime, keep constant relative gain at the CF place.Measurement of flight altitude technology based on playback tone relative amplitude generally requires gain stability.The method and apparatus that the present invention can provide a kind of field that also is suitable for the id reader circuit frequency response to characterize.In an example, generally allow the user to characterize the frequency response at selected frequency place and derive correction coefficient, to eliminate (compensation) change in gain based on loopback channel of the present invention.According to loopback channel of the present invention valuable characteristic can be provided, support low Wei Nami (low-nanometer) measurement of flight altitude.Can come embodiment of the present invention according to optional flying height controlling mechanism and algorithm, perhaps embodiment of the present invention under the situation of the flying height control that lacks activation, perhaps embodiment of the present invention in the measurement that requires accurate flying height sensing is used.

The present invention can provide a kind of method, and this method also is applicable to bit-patterned medium (BPM) record, and the delay of reading in the write paths with the compensation prime amplifier changes.Accurate transformation on the magnetic recording level platform of preformed single position arranges it is the prerequisite of bit-patterned medium (BPM) record.For example, data transfer rate is～4Gbit/ second, and the bit unit is-during 250ps, unite read write in the front amplifier data path～delay of 25ps is changed to the material damage, and makes the exemplary value of conventional disk file prime amplifier.The present invention generally provides the correction coefficient useful to delay compensation technique.Also allow to measure based on loopback channel of the present invention and write data, for example support BPM to the timing of reading data.

With reference to figure 2, but show the diagrammatic sketch of instance of the magnetic recording system environment of embodiment of the present invention embodiment.System 100 can comprise slider 102; Magnetic storage (record) medium 104; Magnetic resistance (MR) reading magnetic head 106; Prime amplifier 108; Flexibility (FOS) transmission line (or element) 110 that dangles; Read/write/loopback module 112; Heater driver 114; Read (record) passage 116; Actuator flexible circuit 118; Variable gain amplifier (VGA) and continuous time filter (CTF) 120; Analogue-to-digital converters (ADC) 122; Digital signal processing (DSP) piece 124; Flying height (FH) controll block 126; Bus 128 and disk drive data controller 130.Read/write/the loopback module 112 of prime amplifier 108 generally comprises reading magnetic head unit, retaking of a year or grade end (public) circuit, write head unit and write-back end (public) circuit.Read/write/loopback module 112 also comprises according to loopback channel of the present invention.Loopback channel allows the user to characterize the frequency response at selected frequency place, and derives correction coefficient, to eliminate change in gain.According to loopback channel of the present invention valuable characteristic is provided generally, supports low Wei Nami measurement of flight altitude.Loopback channel also allows to measure the timing that writes data to reading of data, supports bit-patterned medium (BPM).

Slider 102 is generally apart from rotating recording medium 104 about 2～10nm flights.Slider 102 portability magnetic resistance (MR) reading magnetic heads 106 and write head (not shown).Though the induction reading magnetic head is replaced by the MR type, responds to reading magnetic head and also can be used for the present invention.Slider 102 also carries the well heater that can influence flying height through the thermal deformation of slider 102.Prime amplifier 108 (FOS) transmission line 110 that can dangle through flexibility is connected to magnetic resistance (MR) reading magnetic head 106 and write head.Read/write/loopback electronic circuit 112 and heater driver electronic circuit 114 generally are implemented as the part of prime amplifier 108.Prime amplifier 108 generally is installed in the bottom of the access mechanism (like support arm) that for example passes through the driving of voice coil motor (not shown).Slider 102 can dangle and mechanically be coupled to access mechanism through (also being equipped with FOS's 110 on it) softness.FOS 110 transmits signal at prime amplifier 108 and between the read/write magnetic head element of making on the slider 102 106.

Prime amplifier 108 can be coupled to recording channel 116 through actuator flexible circuit 118.Recording channel 116 is generally handled the magnetic head signal after the amplification through analogue variable gain amplifier (VGA) and continuous time filter (CTF) level (VGA 10 & CTF) 120, so signal (for example, through ADC 122) is digitized.DSP piece 124 is pointed in the output of ADC 122.DSP piece 124 is carried out Data Detection (for example, use iteration or maximum likelihood are handled) and is filtered and extract from the harmonic amplitude of the signal of prime amplifier 108 receptions.The harmonic amplitude of being extracted can be used for flying height and detects.Harmonic wave (tone) amplitude can be sent to FH controll block 126, so that further handle (will hereinafter be described).Can in firmware or hardware, implement flying height controll block 126.Flying height controll block 126 is generally closed the fly-height adjustments loop through heater driver electronic circuit 114.During read operation, the playback of data after string and the conversion is sent to disk drive data controller 130 through the recording channel on the bus 128 116.During write operation, bus 128 will write data and be sent to recording channel 116 from recording controller 130, wherein suitably encode to writing data, to be carved into recording medium 104.

At the conventional double frequency (f that is used for vertical or longitudinal recording ₁, f ₂) in the measurement of flight altitude scheme, detect (f in output place of prime amplifier 108 ₁, f ₂) tone amplitude (for example, measuring in output place of fetch channel ADC122).Handle the amplitude that is detected, to extract flying height information.The typical application of flying height control can be described below: at first, in factory, under specified environment, when magnetic head is on the prerecord calibration region, can allow magnetic head near recording medium surface (being called near the landing point).Then, magnetic head is retreated to predetermined baseline (or flying height set point), measures baseline amplitude herein.The point that lands can carry out sensing through the vibration that superposes on the track position error signal or through auxiliary acoustic sensor or thermal sensor.Because the risk of catastrophic head disk interference process increases, preferably, the middle execution that is absent from the scene is landed and is retreated.

After this,, periodically make magnetic head be back to the prerecord calibration region, and remeasure the harmonic amplitude that flying height place at that time produces at the driver life period.Calculate the flying height error relevant with set point, and after will compensating and the calibration after error be applied to the heater driver in the prime amplifier 108, with fly-height adjustments to set point.Can repeat to remeasure processing in case of necessity.The theory that harmonic amplitude and flying height are interrelated is the basis with famous Wallace's equation; This equation interrelates (referring to H.N.Bertram regenerative process frequency response and magnetic head media spacing; Theory of Magnetic Recording.Cambridge; England:Cambridge University Press, 1994, be hereby expressly incorporated by reference).Because Wallace's equation is invalid in long wavelength's perpendicular recording,, perhaps need proofread and correct basic Wallace's formula so need in calibration region, keep high magnetic flux density.

With reference to following derivation, show the instance that uses Wallace's " space loss " Equation for Calculating magnetic flying height (or spacing).

Wallace's equation as the magnetic head output voltage of the function of head-media yoke distance:

$V=K\·e^{-\frac{2\mathrm{\π}\·x}{\mathrm{\λ}}}=K\·e^{-\frac{2\mathrm{\π}\·f\·x}{v}}$ Equation 1

Wherein, V=| regenerative voltage |; V ≡ Magnetic Head speed; F ≡ frequency; λ=wavelength; K=also is the coefficient of prime amplifier and magnetic head gain to the reason of the variation of frequency; And x=yoke distance/magnetic flying height.

For landing/calibration flight height d _TDTwo selected frequency f 1, f2 (f2＞f1),

The tone amplitude that measurement is associated:

equation 2

equation 3

The value of

and

for good and all is kept in the flash memory of driver for example, so that use in the future.

Subsequently, in operation, when wanting the unknown magnetic flying height of sensing d, can carry out following processing:

Set d=d _TD+ d _ΔAnd measurement f ₁, f ₂The amplitude at place

With

Use the saved landing / calibration values

and and calculate the quotient:

$\frac{V_1^{x=d}}{V_2^{x=d}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA0000076949920000051.png,HDA0000076949920000081.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\&CenterDot;e^{-2\mathrm{\&pi;}{f}_{1}d/\mathrm{<figure-callout\; id="2"\; label="v\; K"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">v</figure-callout>}}}{K_{}}=\frac{[V_1^{x=d_{\mathrm{TD}}}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{2\mathrm{\&pi;}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000076949920000051.png,HDA0000076949920000081.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\&CenterDot;d_{\mathrm{TD}}}{v}}]\&CenterDot;e^{-2\mathrm{\&pi;}{f}_1(d_{\mathrm{TD}}+d_{\mathrm{\&Delta;}})/v}}{[V_2^{x=d_{\mathrm{TD}}}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{2\mathrm{\&pi;}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\&CenterDot;d_{\mathrm{TD}}}{v}}]\&CenterDot;e^{-2\mathrm{\&pi;}{f}_2(d_{\mathrm{TD}}+d_{\mathrm{\&Delta;}})/v}}=\frac{V_1^{x=d_{\mathrm{TD}}}}{V_2^{x={\mathrm{<figure-callout\; id="2"\; label="d\; TD\; e"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{TD}}}}{e}^{}{}^{\frac{2\mathrm{\&pi;}{d}_{\mathrm{\&Delta;}}(f_2-f_1)}{v}};$ And

Find the solution d _Δ

$\&DoubleRightArrow;d_{\mathrm{\&Delta;}}=\frac{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">v</figure-callout>}}{2\mathrm{\&pi;}(f_2-f_1)}\&CenterDot;\mathrm{Ln}[\frac{V_1^{x=d}}{V_2^{x=d}}\&CenterDot;\frac{V_2^{x=d_{\mathrm{TD}}}}{V_1^{x=d_{\mathrm{TD}}}}]$ Equation 4

Note constant d _TDDisappearance

f ₁And f ₂Reader signal path gain rate of change, comprise because the reader input stage is---relevant with the ratio at baseline place---with the flexibility effect that causes alternately of dangling influencing the measurement of flight altitude precision.Need driver in the life-span to differential gain (for example, frequency f ₁And f ₂Relative gain change) limit.Above derivation usually shows from a base measurement of the magnetic flying height of inferring of landing.Range value that is associated with baseline magnetic flying height and tone range value subsequently can be used for confirming the unknown magnetic flying height of driver in the life-span.

With reference to following derivation, show the processing of the simulaed path differential gain variation that quantizes permission.

Can confirm the susceptibility of flying height through following calculating sensitivity function to (the ratio form that the prime amplifier differential gain skew that since landing/calibration, has taken place causes) error:

equation 5

$S_{\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}^d\&equiv;\frac{\mathrm{\&delta;\; d}/d}{\mathrm{\&delta;}\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)/\frac{V_1^{x=d}}{V_2^{x=d}}}=\frac{\frac{V_1^{x=d}}{V_2^{x=d}}}{d}\&CenterDot;\frac{\&PartialD;d}{\&PartialD;\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}=\frac{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">v</figure-callout>}}{2\mathrm{\&pi;}(f_2-f_1)\&CenterDot;d}$ Equation 6

Note $\frac{\&PartialD;d}{\&PartialD;\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}=\frac{\&PartialD;d_{\mathrm{\&Delta;}}}{\&PartialD;\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}=\frac{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">v</figure-callout>}}{2\mathrm{\&pi;}(f_2-f_1)}\&CenterDot;{\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}^{-1}$ Equation 7

The percentage error ε that has allowed during the Ψ percentage error that ∴ allows in the magnetic flying height at spacing d place has implied

$\mathrm{\&epsiv;}=\frac{\mathrm{\&Psi;}}{S_{\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}^d}\%=\frac{\mathrm{\&Psi;}\&CenterDot;2\mathrm{\&pi;}(f_2-f_1)\&CenterDot;d}{v}\%$ Equation 8

In dB, ε _DB=20log ₁₀(1+ ε/100) dB equation 9

$\&DoubleRightArrow;{\mathrm{\&epsiv;}}_{\mathrm{DB}}=20\&CenterDot;{\mathrm{Log}}_{10}(1+\frac{\mathrm{\&Psi;}}{100}\&times;\frac{2\mathrm{\&pi;}(f_2-f_1)\&CenterDot;}{v})$ Equation 10

Instance:

Consider 3.5 inches, the 7200RPM/120RPS disc driver has 3Gbit/ OD second maximum transfer rate and magnetic flying height d～6nm.

OD radius～1.6 " (0.041m)

f=DR/2.

For f ₁And f ₂, reasonably be chosen as f ₁=f/8; f ₂=3f/8.

$\&DoubleRightArrow;f=1.5e9\mathrm{Hz},$ ${\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000076949920000051.png,HDA0000076949920000081.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\&cong;375\mathrm{MHz};$ ${\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\&cong;1125\mathrm{MHz}.$

The dB differential gain of obtaining permission changes, with flying height error Ψ≤10% of guaranteeing to measure

$S_{\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}^d\&equiv;\frac{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="HDA0000076949920000121.png"\; state="\{\{state\}\}">v</figure-callout>}}{2\mathrm{\&pi;}(f_2-f_1)\&CenterDot;d}\&ap;1.1,\mathrm{\&epsiv;}\&equiv;\frac{\mathrm{\&Psi;}}{S_{\left(\frac{V_1^{x=d}}{V_2^{x=d}}\right)}^d}\&ap;\&PlusMinus;9.1\%,$

Calculate and the corresponding dB gain error of positive and negative flying height error respectively:

-0.83dB≤ε _dB＝20·log ₁₀(1+ε/100)dB≤+0.76dB

The above-mentioned magnetic flying height that illustrates is calculated to expand to and is quantized to cross over the long-run gains rate precision specification of passing the whole simulation system of recording channel simulaed path (for example VGA & CTF piece 120) from MR magnetic head 106.In an example, specify the restriction of the necessary differential gain skew of measurement of flight altitude precision can use the processing shown in the above-mentioned derivation to confirm for realizing.Above-mentioned derivation usage example property value shows the The Application of Technology of above-mentioned derivation.

With reference to figure 3, show curve map, this curve map show expression fixing ± maximum of 10% magnetic flying height error allows difference gain error ε _DBCurve plotting A-L; In this case, for 7200RPM, magnetic head is arranged near 3.5 inches disks the OD.Susceptibility (Sd) can be confirmed according to equation 6.Error (± dB) can confirm according to equation 8～equation 10.For example, can read the curve map of Fig. 3, be that DR=3Gbit/ second and typical value are f so that data transfer rate to be shown ₁=DR/8 and f ₂=3DR/8 place, system's differential gain error of permission should be no more than～± 0.58dB, with the magnetic flying height of support～4.5nm do.The flying height of curve map A-L and frequency values are summarised in the following table 1:

Table 1

Though shown in coefficient can represent the coefficient supported in the typical record passage.But other coefficients can be used for satisfying the design standards of specific implementations.Point M mark the position on the curve C, this location tables shows that data transfer rate is 3005Mbits/ second, flying height is that 4.5nm and maximum allows the difference gain error to be ± 0.58dB.Point N mark the position on the curve E, this location tables shows that data transfer rate is 3000Mbits/ second, flying height is that 3.5nm and maximum allows the difference gain error to be ± 0.46dB.Point O mark the position on the curve J, this location tables shows that data transfer rate is 3000Mbits/ second, flying height is that 2nm and maximum allows the difference gain error to be ± 0.26dB.

4.5nm the magnetic flying height is being increased to 1Tbit/in ²In the required scope of recording density.For ± 0.58dB system differential gain error; Give combined preamble amplifier read/write/loopback module 112, flexibility dangle transmission line 110 and 106 cascades of MR magnetic head distribute～± the 0.5dB error is rational; But, in conventional reader, be difficult to usually reach.Remaining～± the 0.08dB error can consume in the analog processing circuit (for example, VGA&CTF piece 120) of recording channel 116, and the quantizing noise among the conduct ADC 122 that is associated.The present invention generally provides other scheme of level that can " proofreading and correct the back " error be reduced to permission.

With reference to figure 4 (block diagram), show block diagram, to illustrate the illustrative embodiments of the prime amplifier 108 among Fig. 2 according to an illustrative embodiment of the invention.In an example, prime amplifier 108 can be embodied as the multihead prime amplifier.For clear, omitted heater driver element 114.According to the embodiment of the present invention, prime amplifier 108 can comprise read path circuit 130, write paths circuit 132, loop-back path (or passage) 134, terminal 136 and terminal 138.The path circuit 130 that normally reads of prime amplifier 108 comprises input stage (or circuit) 140 (for example, reading magnetic head unit) and gain stage (or circuit) 142.Normal read data path also comprises MR reading magnetic head 106 and flexibility (FOS) assembly 110 that dangles.In order to simplify, input stage 140 is incorporated the read/write/loopback module 112 among Fig. 2 into gain stage 142.The quantity of input stage 140 can equal the magnetic head number on the driver.Gain stage 142 can provide the user-programmable gain with the typical range from～12dB to～42dB jointly.Gain stage 142 also can provide programmable frequency response shaping.But gain stage 142 common service are in input stage 140.Can in input stage 140, accomplish the termination of FOS 110.Input stage 140 can merge the MR biasing circuit, so that the MR magnetic head 106 that is associated is offset to the optimal operations point.After handling, can show the read back waveform (for example, RD OUT) after the amplification on the terminal 136, the transmission that is used to go to the fetch channel 116 on the flexible circuit 118.Can difference form show after amplifying read back waveform RD OUT (for example, RDP/RDN).

The write paths circuit 132 of prime amplifier 108 generally starts from terminal 138.In an example, terminal 138 can write data (for example, WD IN) via the low amplitude of oscillation difference that flexible circuit 118 receives from the write device circuit (not shown in figure 1) of recording channel 116.The data that write of input are passed through receiver and Signal Regulation level 150, through write driver (write head unit) 152, arrive FOS 154 and induction write head 156 then.Can incorporate a plurality of write elements that read into prime amplifier 108.A plurality of write elements that read allow single silicon to serve a plurality of magnetic heads.In an example, prime amplifier 108 can comprise magnetic head selection bus 158.Magnetic head is selected bus 158 to can be used for being controlled at which bar of fixed time activation and is read write paths.

The loop-back path of prime amplifier 108 (or passage) 134 can be coupled to read path circuit 130 and the (ii) write paths circuit 132 between receiver and Signal Regulation level 150 and the write driver 152 between (i) input stage 140 and the gain stage 142.In an example, the input of loop-back path 134 can be coupled to the output of receiver and Signal Regulation level 150, and this output can be coupled to the input of gain stage 142.In an example, loop-back path 134 can comprise piece (or element) 160, piece (or element) 162, piece (or element) 164 and piece (or element) 166.Element 160,162,164 and 166 is new-type elements of the present invention.Usually activation block 160,162,164 and 166 only is used for the loopback compensation calibration.During the loopback compensation calibration, forbidding input circuit 140.If in the write operation process, carry out the loopback compensation calibration, can keep launching one or more write heads unit 152.If carry out the loopback compensation calibration separately, then can make all write driver 152 outages.In an example, magnetic head selects bus 158 to encode to echo command, perhaps can use other mode tag, to launch loopback channel 134 and to forbid input stage 140 and write driver 152.

In an example, piece 160 can be embodied as simplification (illusory) form of reader input stage 140.Piece 160 here is commonly referred to as and reads loopback cell (or circuit).In order to simplify and reduce power consumption, for example, read loopback cell 160 and can omit the MR biasing circuit of incorporating normal reader input stage 140 into.As long as read the response that loopback cell 160 is fully duplicated input stage 140, just can from read loopback cell 160, delete other characteristics in the normal reader input stage 140.For example, input stage 140 with read loopback cell 160 and should have similar input structure.

In an example, piece 162 can be embodied as current switching circuit.Usually, piece 162 provides variable amplitude current-mode differential signal to drive to reading loopback cell 160.Amplitude control able to programme (for example, from the register field in the steering logic of prime amplifier 108) can allow the user to select to guarantee the driving rank of prime amplifier 108 outputs in the range of linearity of performance on the terminal 136.For offsetting the influence of the optional gain in the reader gain stage 142, the expectation programmability.In an example, can adopt routine techniques current switch 162 to be embodied as electric current route (current-routing) long-tail pair with programmable variable tail current source.

In an example, piece 164 can be embodied as selector circuit.In an example, piece 166 can be embodied as the write driver unit (or circuit) of simplification (illusory).Piece 166 here is commonly referred to as and writes loopback cell (or circuit).Usually, piece 164 is reconciled from 162 inputs of one current switch in two sources: write data sink and Signal Regulation level 150 or write loopback cell 166.When carrying out the loopback timing, can select to write data sink and Signal Regulation level 150 for measuring flying height.When being the compensation of delay execution loopback in the BPM system, can select to write loopback cell 166.The frequency response of selector switch 164 and current switch 162 should be smooth, to surpass the test frequency of expectation.

According to instruction of the present invention, read loopback circuit 160 and be parallel to input stage 140 and be added effectively and be configured to, make the output of the output replacement input stage 140 that can under user's control, select to read loopback circuit 160.Equally, being parallel to write driver 152 is provided with effectively and writes loopback circuit 166.In an example, control down the user, write loopback circuit 166 and can point to the input of reception from terminal 138, in this case, the write device driver 152 of any amount still can drive through the output of piece 150.Read loopback circuit 160 and write loopback circuit 166 and be connected with variable gain block 162 through switch 164.

Generally speaking, comprise that the loopback driver 166 that writes in the loopback actuation path is unnecessary during flying height loopback compensation calibration, because the pulse asymmetry can influence the loopback harmonic amplitude of being extracted.Use for BPM, will add writing loopback cell 166 and incorporate in the loopback actuation path.Usually, write the operation of the normal write driver of loopback cell 166 simulations unit 152, even, keep time-delay simultaneously to the temperature characterisitic of normal write driver unit 152 at low inner amplitude of oscillation place.Like this, BPM loopback operation can be measured the delay that writes data routing input terminal 138 to read data path lead-out terminal 136.When flying height correction loopback is effective, can forbid write driver 152, write to prevent being not intended on the storage medium.During the BPM loopback, can forbid all write drivers 152; Alternatively, but one or more write drivers 152 can be effectively, to allow the dynamic calibration that writes the clock phasing during write operation.

In order to use echoplex technique according to the present invention to confirm the differential gain corrected value, comprise f ₁, f ₂The Serial No. of frequency component is applied to usually and writes data routing input terminal 138.Analyze the read data path output (for example) on the terminal 136 then, to confirm f through the DFT in the recording channel (DFT) ₁, f ₂The relative amplitude of component.Alternatively, simple f ₁Or f ₂But tone continuous drive to terminal 138, and reuse the DFT technology and carry out twice measurement, because current switch 162 all is the high-gain current mode circuit with PECL receiver 150.Should after the landing base measurement, carry out echo program immediately, to obtain the initial loopback baseline response that is permanently stored in the driver memory.When measuring flying height, can carry out follow-up echo program.The correction that the prime amplifier relative gain changes can give poor between (preservation) baseline and the follow-up return result.

Usually, measure the effect that impliedly comprises flexible circuit 118 and tunnels analogy chain 120 according to prime amplifier loopback of the present invention.This is useful, has avoided the needs of the independent local echoing calibration of tunnels analogy chain.Generally speaking, echo program can not receive the terminal mismatch affects that the variation of FOS/Zin mismatch causes.Therefore, the prime amplifier of implementing according to the present invention should provide the broadband input impedance to temperature stabilization.At selected flying height test frequency f ₁, f ₂The place, the relative response of series connection FOS/ input stage or current/voltage transition net is not taken in significant change takes place in the life of product.

With reference to figure 5, show the diagrammatic sketch of the embodiment of the prime amplifier 108 among sets forth in detail Fig. 4.In an example, the loopback circuit 134 of piece can be arranged in piece (or circuit) 170, piece (or circuit) 172, piece (or circuit) 174 and the piece (or circuit) 176.Usually, piece 170 and 172 is similar to and reads loopback cell 160 among Fig. 4.Usually, piece 174 is similar to the piece 162 and 164 among Fig. 4.Usually, piece 176 is similar to and writes loopback cell 166 among Fig. 4.In an example, piece 170 can be used as illusory loopback common mode zero circuit.In an example, piece 172 can the fact be illusory (loopback) reading unit.In an example, piece 174 can truely be loopback injection and gain control circuit.In an example, piece 176 can the fact be illusory (loopback) write device circuit.

Piece 170 can comprise output zero clearing and the common mode control circuit that is associated with illusory reading unit 172.The circuit of piece 170 can be used for guaranteeing that the static shift in the illusory reading unit 172 can too not drive reader rear end gain stage 142.Can similar skew-clear circuit be set about reading magnetic head unit 140.When this clear circuit was set, the clear circuit that is associated with reading magnetic head unit 140 and illusory reading unit 172 can merge.In an example, loopback injection and gain control block 174 can comprise the selector switch piece 164 and current switch piece 162 of the Fig. 4 that combines.Selector switch piece 164 can combine with current switch piece 162, and is uncertain to reduce the propagation delay that increases when the circuits cascading.Piece 176 can comprise be used for that the BPM path delay measures write loopback cell 166.

With reference to figure 6, show the diagrammatic sketch of the illustrative embodiments of the loopback piece 134 of illustrating among Fig. 5.Circuit shown in Fig. 6 usually shows according to an illustrative embodiment of the invention.Those of ordinary skills can understand also optional implementation to be arranged when reading the instruction that comprises here.In an example, preferably use complementary SiGe BiCMOS to handle (bipolar junction transistor combines with complementary metal oxide semiconductor techniques).But under the situation that does not deviate from specified scope of the present invention, other technologies can be used for implementing loopback piece 134.In an example, can use the Origami cascaded loopback piece 174 of implementing of complementary bipolar.Loopback injection and gain control block 174 merges the functions of selector switch pieces 164 and variable amplitude current switch piece 162 usually, and be uncertain to reduce the propagation delay that increases when the circuits cascading.

In an example, combination selection device and variable amplitude current switch piece 174 can be sent to the current-mode signal resitstance voltage divider 176 of loopback reading unit 172.Usually, resitstance voltage divider 176 simulation MR magnetic heads.The cen-tral electric resistor of resitstance voltage divider 176 can be low value, and for example, 5 Ω allow to utilize loopback to inject the device current density of switch 174 abundances, come the optimised devices response time with the device through operation set electrode current output maximal value Ft or Fmax place.Current switch 174 can comprise the tail current mirror (like the I ampere) of variable intensity, thereby allows the control loopback to inject rank.As previously mentioned, preferred this control is so that the gain setting in the reader part of compensation prime amplifier changes.(pnp) Origami cascaded emitter source can be subordinated to intensity 2I.Operation transconductance amplifier (OTA) 178 can be set up common mode ground connection in illusory reading unit 172, and output is being applied to gain stage 142 output of zero clearing reading unit before.The capacitor of output place that can be through being coupled in OTA 178 provides loop compensation.OTA 178 can be independent of the OTA that comprises in the MR bias control circuit of reader input stage 140, perhaps can merge with it.Because high zero point precision and instantaneous recovery time are not necessary factor in loop back mode, so OTA 178 can adopt simple designs.

In an example, can illusory reading unit 172 be configured to have the common grid topology that input impedance (like Zin) is set up in the tail source, to mate the common grid/cross-coupled common gate structure of main prime amplifier.Illusory fetch stage 172 can be adopted the equivalent of equal parallelly connected feedback differential common emitter form.But, can implement other illusory level designs, to mate the input stage of specific main prime amplifier.

With reference to figure 7, illustrate circuit 108 ' diagrammatic sketch, to illustrate another exemplary prime amplifier of implementing according to alternative embodiment of the present invention.The piece of identical numbering and the corresponding blocks among Fig. 4 have same function.Circuit 108 ' omitted the complete illusory loopback circuit 134 among Fig. 4 helps a plurality of independent and less bridge joint loopback cell, 134a-134n.The bridge joint loopback cell that each is less, 134a-134n, all with Fig. 4 in unit 134 have analog structure.Each bridge-jointing unit, 134a-134n can serve a pair of read/write magnetic head unit (for example, 140a and 152a, 140b and 152b etc.).Be to reduce complicacy, can be from each write head unit 152a-152n IT signal (shown in 182), and be driven to each reading magnetic head unit 140a-140n (shown in 180).Though show between the read/write magnetic head that bridge joint loopback cell 134a-134n is coupled in similar numbering, the specific read/write magnetic head that is coupled by given bridge joint loopback cell is not crucial.Through implementing a plurality of bridge joint loopback cell 134a-134n but not single loopback circuit 134 is as shown in Figure 4, loop-back path comprises than the more read/write data routing of the embodiment of Fig. 4.The result is that loopback relevant with the embodiment shown in Fig. 4 and the coupling between the data transfer path obtain useful improvement.In addition, because the proximity of loopback in the embodiment of Fig. 7 and read/write magnetic head unit, so lower than Fig. 4 implementation in Fig. 7 implementation of the thermic parameter drift between loopback and the data routing.

Also show exemplary reading magnetic head unit 140x among the figure, illustrated first input that bridge joint loopback cell 134a-134n can be connected to output element 184, other circuit 186 of reading magnetic head unit can be connected to second input of element 184.In addition, also show exemplary write head unit 152x among the figure, illustrated bridge joint loopback cell 134a-134n and can be connected the shift component 187 of write head unit 152 and write between the bridging element 189.

With reference to figure 8, show the diagrammatic sketch of the embodiment of the prime amplifier 108 ' among sets forth in detail Fig. 7.In an example, element 106,110,138,140,142,146,150,152,154 and 156 element that can be similar to the similar numbering of Fig. 5 is implemented.As shown in Figure 5, write head unit 152 can match with reading magnetic head unit 140.Can introduce loopback channel through bridgt circuit part 190,192,194,196 and 198. Loopback bridging part 190 and 192 only is used for bit-patterned medium recording.Part 190 can receive from the input that appears at the level shifter 187 in the write device unit 152 usually.Part 192 can receive the input from PECL receiver 150.In an example, the signal from PECL receiver 150 can be cushioned by part 196.Part 190 can be configured to convert cmos signal into differential signal.In an example, part 192 can be embodied as the AOI grid.

Part 190 provides the delay of following the tracks of approx through the delay of write device output driver 189.Can be through the selection between AOI grid 192 completion bit patterned medias and the flying height loop back mode.AOI grid 192 is general corresponding to the switch among Fig. 7 164.The AOI grid receives the input from PECL receiver 150, and transmits the signal to part 196.Part 196 general reading section 134a-134n corresponding to the bridge joint loopback circuit among Fig. 7.Part 198 is injected reading magnetic head unit 140 with backhaul signals.Comprise part 190,192 and 194 the loopback bridge-jointing unit can with every pair read the write head unit, 140a-140n and 152a-152n are associated.

Can accomplish the zero clearing of biasing of input place of amplifier 142 through part 198.Part 198 can be embodied as zero clearing loop OTA and capacitor.Part 198 is injected part 194 with electric current, with the biasing of amplifier 142 inputs place servo be zero.MR biasing Control and Feedback loop can be multiplexed to accomplish zero clearing, need not the zero clearing element 198 that provides independent.

Another kind distortion according to of the present invention bridge joint scheme is used for making the input amplifier 184 of reading magnetic head unit 140 to keep biasing fully, and suppresses the biasing of MR magnetic head.Cancellation activates the biasing of MR magnetic head can suppress the magnetic head read back waveform usually, makes the loopback dominate, reduces the complicacy of skew clear circuit simultaneously.According to another distortion of bridge joint scheme of the present invention, bridge joint loopback cell 134a-134n can adopt (its output is directly injected each reading magnetic head unit 140a-140n's with electric current) simple current switch long-tail pair.The attractive force of this method is its simplicity.But, need in microampere loopback injection circuit, have the bipolar of enough Ft or MOSFET device.

With reference to figure 9, show the diagrammatic sketch of the illustrative embodiments of illustrating loopback gain circuitry 200.Circuit 200 can be used for implementing the loopback gain block 194 of Fig. 8.The grounded-base transistor QA zero clearing electric current injection loopback level that allows squint.Activator switch injects to select loopback.In an example, switch can be in response to signal (for example, ENABLE LOOPBACK) Be Controlled.In an example, switch can be embodied as nmos device.Through a plurality of switches are set, can between a plurality of reader unit, share single loopback cell on every support arm.Power supply IL is mated.Therefore, there is not electric current to flow into nmos source from power supply IL.Therefore, only through the power supply IX nmos device of setovering.Power supply IL sets the loopback gain through the switching current that control generates the voltage that strides across resistor R 1.Resistor R 1 is generally smaller value (for example, 5-20 ohm).Resistor R 2 generally is configured near the resistance of MR magnetic head (for example, each～200 ohm).The voltage source that the grid of nmos device generally is connected to the Vgs (on) that follows the tracks of NMOS common gate level (for example ,+Vgson).Like this, make CG NMOS output become～0V.

With reference to Figure 10, show the diagrammatic sketch of circuit 210, illustrated illustrative embodiments according to reading magnetic head of the present invention unit.Reading magnetic head element circuit 210 can be used for implementing the piece 140 of Fig. 8.According to the present invention; Circuit 210 can be implemented with like the conventional reading magnetic head unit class; Remove NOT-circuit 210 and can comprise that (i) (for example is used for CC 210 to loopback level; Circuit 200) tie point (for example, circuit 200) and (ii) be configured at normal mode (for example, conventional reading magnetic head unit) and the switch of commutation circuit 210 between according to loop back mode of the present invention.In an example, switch can be embodied as nmos device.Switch can cooperate the similar switch in the loopback level to work.In an example, can cancel activator switch, to select loop back mode.In an example, switch can be in response to signal (for example ,～ENABLE LOOPBACK) and Be Controlled.In an example, but signal～ENABLE LOOPBACK compensating signal ENABLE LOOPBACK.

With reference to figure 11A, show the diagrammatic sketch of circuit 220, illustrated the illustrative embodiments of the loopback clear circuit that comprises operation transconductance amplifier (OTA).Circuit 220 can be used for implementing the zero clearing piece 198 among Fig. 8.Circuit 220 can be configured to generate the reading magnetic head unit bridges connecting to neutral signal that can be provided for all magnetic head units.Circuit 220 can be configured to generate reading magnetic head unit bridges connecting to neutral signal based on read output signal (for example, NULLPOINT SENSE) and reference signal (for example, CURRENT_SWITCH CM REF).

With reference to figure 11B, show the diagrammatic sketch of circuit 230, illustrated another illustrative embodiments of loopback clear circuit.Usually, circuit 230 is the reduced form of circuit 220.For example, circuit 230 has been deleted an OTA, two nmos devices, a capacitor and two resistors.OTA and PMOS differential pair are as DC voltage zero clearing loop, to remove the static shift from the input of the gain stage in the gain stage in the reader gain stage.Select capacitor, with compensation feedback loop.

With reference to Figure 12, show histogram, illustrated the differential gain error that has and do not have according to prime amplifier, FOS and the MR magnetic head of loopback compensation of the present invention.The bar post of shade is represented uncorrected differential gain error.According to the present invention, the bar post of white representes to utilize the correction differential gain error of loopback compensation acquisition.Covered 30% to 60% relative humidity, corresponding to the interior humidity (humidity effect FOS Kapton dielectric

) of the HDA that uses drying agent.Show the typical scope of industrial environment and be prime amplifier chip temperature from-1 ℃ to 139 ℃.Arrow magnetic head 280 on the horizontal ordinate mid point defines the initial landing carrying out factory and carry out/the retreat environmental baseline of measurement.It is DR=3Gbit/ second and f that light color bar post is illustrated in data transfer rate ₁=DR/8, f ₂=3DR/8 place has the 7200RPM that is arranged near the magnetic head OD (r=1.6 inch), (for example, use loopback compensation) result after the correction of 3.5 inches drivers.Compared to the not corrected value of stressing by dark-coloured bar post, relative f ₁, f ₂The differential gain error reduces～60%, shows that the prime amplifier of proofreading and correct according to the present invention can be at following 1Tb/in ²In the register system for admissible the measurement of flight altitude at～2nm place～± 0.18dB differential gain error.

With reference to Figure 13, show process flow diagram, illustrated the processing 300 that comprises the double frequency measurement of flight altitude technology of loopback compensation according to of the present invention.Handle 300 supposition in factory's executed measurement of landing/retreat.Therefore, handle 300 and be illustrated in flying height calibration and the control sequence of regularly carrying out in the disc driver life-span.Usually, run through the execution regularly of driver life-span and handle (method) 300.Method 300 generally comprises step (or state) 302, step (or state) 304, step (or state) 306, step (or state) 308, step (or state) 310, step (or state) 312 and step (or state) 314.Can use prime amplifier 108 implementation methods (or processing) 300.Usually, all amplitude measurements are all represented with decibel (dB).Though for clear, the fully differential gain calibration is shown in step 308 place and is applied in, loopback is proofreaied and correct can be separated and after each loop back test, carrying out local equalize immediately.General with a kind of method preservation in back storer.

In step 302, handle 300 beginnings.In step 304, magnetic head is return prerecorded calibration region, and measures (for example, measuring in output place of fetch channel ADC 122) current flight height (for example, d in output place of prime amplifier 102 ¹) two (for example, f of locating to take place ₁, f ₂) tone playback amplitude.Measured value can be described as (being expressed as) A _F1And A _F2In step 306, set (launching) loop back mode, and with compound f ₁, f ₂Sequence is injected into and writes on the data line.When with compound f ₁, f ₂Sequence is injected into when writing on the data line, f ₁, f ₂The amplitude of component is write down (for example, fetch channel ADC 122 output place).The amplitude of record can be described as A _F1 ^LoopbackAnd A _F2 ^LoopbackExpression.In step 308, can use predetermined (for example, factory set) baseline playback and baseline loopback value (for example, A _F1 ^{Proofread and correct}=A _F1-(A _F1 ^Loopback-A _F1 ^{The loopback baseline}), and A _F2 ^{Proofread and correct}=A _F2-(A _F2 ^Loopback-A _F2 ^{The loopback baseline})) come the playback amplitude behind the calculation correction.In step 310, can use Wallace's Equation for Calculating and set point d _BL: ε=d _BL-d ¹Relevant flying height error.In step 312, the ε after compensation back and the calibration can be applicable to the heater driver 114 in the prime amplifier 108, controls to the d of set point _BLFlying height.In step 314, handle 300 and can finish.But, but re-treatment in case of necessity 300 (for example, repeatedly iteration).

With reference to Figure 14, show process flow diagram, illustrated and measured the processing 400 that comprises the baseline parameter that uses in the double frequency measurement of flight altitude technology of loopback compensation according to of the present invention.Handle 400 and generally occur in factory, comprise that there the device with the double frequency measurement of flight altitude that compensates according to loopback of the present invention is made or tested.Handle 400 in factory, to prevent the chance of head disk interference aspect unintentionally.Handling 400 is preconditions of carrying out (top describe with reference to Figure 10) processing 300.Method 400 generally comprises step (or state) 402, step (or state) 404, step (or state) 406 and step (or state) 408.Can use prime amplifier 108 manners of execution (or processing) 400.

In step 402,400 beginnings of baseline parameter measurement processing.In step 404, under specified environment, when magnetic head was on prerecorded calibration region, the adjustment magnetic head was retreated to baseline/set point flying height (for example, the d of expectation with near " landing point " then _BL).In the baseline/set point flying height of expectation, at two (for example, f of output place detection (for example, measuring) of prime amplifier 108 in output place of fetch channel ADC 122 ₁, f ₂) amplitude of tone, and forever save as A _F1 ^BaselineAnd A _F2 ^BaselineIn step 404, set loop back mode immediately, and with compound f ₁, f ₂Sequence is injected into and writes on the data line.When with compound f ₁, f ₂Sequence is injected into when writing on the data line, with f ₁, f ₂It is A that the amplitude of tone is write down (for example, fetch channel ADC 122 output place) _F1 ^BaselineAnd A _F2 ^Baseline, and be stored.In step 408, handle 400 and finish.

Those skilled in the art should be understood that; After programming according to this instructions, can use the performed function of diagrammatic sketch: conventional general processor, digital machine, microprocessor, microcontroller, RISC (Reduced Instruction Set Computer) processor, CISC (CISC) processor, SIMD (single instruction multiple data) processor, signal processor, CPU (CPU), ALU (ALU), video digital signal processor (VDSP) and/or similar calculation element with lower device execution graph 10 and Figure 11.Those skilled in the art it is also to be understood that skilled programmer can prepare suitable software, firmware, coding, program (routine), instruction, operational code, microcode and/or program module according to instruction of the present invention.Usually the one or more processors by the machine embodiment come executive software from medium or a plurality of medium.

The present invention also can be through preparation ASIC (special IC), platform ASIC, FPGA (field programmable gate array), PLD (PLD), CPLD (CPLD), sea of gates, RFIC (RF IC), ASSP (Application Specific Standard Product) or through the network interconnection of conventional element circuitry is implemented; As described here, its modification will be readily apparent to persons skilled in the art.

Therefore, the present invention also can comprise it can being the computer product of (comprise and can be used for machine is programmed to carry out the instruction according to one or more processing of the present invention or method) storage medium or medium and/or transmission medium or medium.Come the instruction that comprises in the object computer product and operate peripheral circuit through machine, can be with importing one or more signals that data-switching becomes the one or more files on the storage medium and/or representes physical object or material (such as audio frequency and/or video presentation).Storage medium can include but not limited to that dish (comprising floppy disk, hard disk, disk, CD, CD-ROM, DVD and magneto-optic disk) and the circuit of any kind are (such as ROM (ROM (read-only memory)), RAM (RAS), EPROM (electrically programmable ROM), EEPROM (electrically-erasable ROM (EEROM)), UVPROM (ultraviolet can be wiped ROM), flash memory, magnetic card, light-card and/or be suitable for the medium of any kind of store electrons instruction.

Element of the present invention can constitute a part of or whole of one or more devices, unit, assembly, system, machine and/or equipment.Device can include but not limited to server; Workstation; Storage array controllers; Storage system; PC; Kneetop computer; Notebook computer; Palm PC; Personal digital assistant; Portable electric appts; The battery-powered device; STB; Scrambler; Demoder; Code converter; Compressor reducer; Decompressor; Pretreater; Preprocessor; Transmitter; Receiver; Transceiver; Cryptochannel; Cell phone; Digital camera; Location and/or navigational system; Medical Devices; Head-up display; Wireless device; Audio recording; Storage and/or playback reproducer; Video record; Storage and/or playback reproducer; Gaming platform; Peripherals and/or multi-chip module.It will be understood by those skilled in the art that element of the present invention can be used for the device of other types, to satisfy the standard of application-specific.

Though specifically illustrate and described the present invention with reference to its preferred implementation, it will be understood by those skilled in the art that on the various forms with details on modification do not deviate from scope of the present invention.

Claims (10)

1. device comprises:

One or more reading magnetic head element circuits are configured to via one or more reading magnetic heads from the magnetic medium reading of data, and wherein, said reading of data is present in the read back waveform after the amplification;

One or more write head element circuits are configured to via one or more write heads data write said magnetic medium; And

Loopback channel is coupled between said one or more reading magnetic head element circuit and the said one or more write head element circuit.

2. device according to claim 1, wherein, said loopback channel comprises:

The loopback reader unit is connected to said one or more reading magnetic head element circuit; The luffing current switch is connected to said loopback reader unit; And

Selector unit is connected to said luffing current switch and said one or more write head element circuit.

3. device according to claim 2, wherein, said loopback channel also comprises:

The loopback writing unit is connected to said selector unit and said one or more write head element circuit.

4. device according to claim 2, wherein, said luffing current switch comprises electric current route long-tail pair.

5. device according to claim 1, wherein, said loopback channel comprises:

The loopback reader unit is connected to said one or more reading magnetic head element circuit; And

Loopback injection and gain control circuit are connected to the write paths of said loopback reader unit and said device.

6. device according to claim 5, wherein, said loopback channel also comprises:

A pair of operation transconductance amplifier, being configured to provides common mode ground connection to said loopback reader unit, and is offering the output of zero clearing loopback cell passage before of said one or more reading magnetic head element circuit.

7. device comprises:

One or more id reader circuit are configured to from the magnetic medium reading of data;

One or more write device circuit are configured to data are write to said magnetic medium; And

Loopback channel is coupled between said one or more id reader circuit and the said one or more write device circuit, and wherein, said loopback channel uses complementary SiGe BiCMOS to handle and implements.

8. method may further comprise the steps:

Measurement is read the prerecord calibration region of magnetic storage medium simultaneously in the amplitude of two frequencies of output place of prime amplifier;

Launch the loop back mode of said prime amplifier, and inject the Composite Double frequency sequence on the data line writing of said prime amplifier;

When said Composite Double frequency sequence is injected on the said write data line of said prime amplifier, be recorded in the amplitude of two frequencies of output place of said prime amplifier; And

Use the playback amplitude after amplitude that (i) measure, the amplitude that (ii) writes down in the loop back mode and (iii) predetermined baseline loopback value are come calculation correction when reading said prerecord calibration region.

9. device comprises:

One or more id reader circuit are configured to from the magnetic medium reading of data;

One or more write device circuit are configured to data are write said magnetic medium; And

Loopback channel; Be coupled between said one or more id reader circuit and the said one or more write device circuit; Said loopback channel comprises the loopback injection and the gain control circuit of loopback reader unit that is connected to said one or more id reader circuit and the write paths that is connected to said loopback reader unit and said device; Wherein, said loopback injection and gain control circuit comprise the Origami cascaded circuit of complementary bipolar.

10. device comprises:

One or more id reader circuit are configured to from the magnetic medium reading of data;

One or more write device circuit are configured to data are write said magnetic medium; And

Loopback channel; Be coupled between said one or more id reader circuit and the said one or more write device circuit; Wherein, Said loopback channel comprises: be connected to the loopback reader unit and a pair of operation transconductance amplifier of said one or more id reader circuit, said operation transconductance amplifier is configured to said loopback reader unit common mode ground connection is provided, and is appearing at the output of the said loopback channel of zero clearing before of said one or more id reader circuit.

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